linux-ext4 - Re: [PATCH] ext4: take i_mutex in ext4_symlink to eliminate a warning from ext4

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Message-ID: <20130327151248.GE14900@thunk.org>
Date:	Wed, 27 Mar 2013 11:12:48 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	linux-ext4@...r.kernel.org, Zheng Liu <wenqing.lz@...bao.com>
Subject: Re: [PATCH] ext4: take i_mutex in ext4_symlink to eliminate a
 warning from ext4_truncate

On Wed, Mar 27, 2013 at 11:19:22PM +0800, Zheng Liu wrote:
> > > Otherwise, couldn't we end up with problems where a failed write calls
> > > ext4_truncate() without i_data_sem(), and that races with something
> > > else --- say, a punch or truncate call to that same inode?
> 
> Let me think about it.  I need to take a close look at it.

Note that I'm not so concerned when we are creating symlink --- you
are quite right in pointing out in that case the inode isn't in the
namespace yet, so that prevents races --- but also what might happen
in an ENOSPC write(2) failure racing against a punch/truncate call.

But again, this is why I added the warning --- it was to find these
edge cases that we might not have considered.  :-)

     	   	   	     	  	       - Ted
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